The invention relates to polishing devices, e.g., for producing flat surfaces on wafers of semiconductor materials.
Integrated circuits often are formed on a flat surface of a wafer made of a semiconductor material such as gallium arsenide or indium phosphide. Calawa et al., U.S. Pat. No. 4,323,422, describes a polishing device for producing a flat, damage free surface on such wafers. The device has a polishing wheel, a sample mounting block carrying a plurality of wafers and positioned so that the surface of the wafer is adjacent to a portion of the wheel, and a spout for supplying polishing fluid to the center of the wheel. As the wheel rotates, the fluid is spread across the surface of the wheel by centrifugal force. The rapidly moving fluid lifts the wafers such that the wafers and the polishing wheel do not contact each other, i.e., the samples hydroplane on the fluid. The fluid forces on the samples cause the holder to rotate.
It has been proposed prior to my invention that a semiconductor wafer can be made to hydroplane by introducing a polishing fluid under pressure through openings in the polishing wheel. It also has been proposed that this approach be implemented by using a stationary polishing wheel having a band of holes through which fluid is supplied by means of an annular recess located on the underside of the wheel. The proposed device further has two sample holders--each suitable for supporting one wafer--connected by an arm that moves the holders over the band; the holders are supported in the arm by air bearings.